Loft Conversion Quotes For Free

Find Trusted Loft Conversion Specialists Near You

A loft conversion is usually the cheapest way to add a bedroom to a house you already own. CompareTradeQuotes matches you with local loft conversion specialists, staircase fitters, loft ladder and boarding installers and insulation companies. Get up to 3 free, no-obligation quotes and compare before you commit.

How Much Does a Loft Conversion Cost?

Cost is driven mainly by type — how much of the existing roof has to change. A rooflight conversion runs £25,000 – £40,000, a rear dormer £30,000 – £65,000, a hip-to-gable £33,000 – £70,000 and a mansard £38,000 – £90,000. An en-suite adds £6,000 – £15,000. London and the South East add 20–30%.

Not every loft job is a conversion, and the smaller ones cost a fraction of that. Loft insulation is £700 – £1,200, loft boarding £70 – £100 per m², and a loft ladder fitted to an existing hatch is £250 – £400.

Full loft cost breakdown

Indicative UK ranges, July 2026.

Job	Typical UK cost (2026)	Notes
Rooflight / Velux-style conversion	£25,000 – £40,000	No change to the roof shape — needs existing head height
Rear dormer	£30,000 – £65,000	Most common type. Terraced rear dormer typically £40,000 – £55,000
Hip-to-gable	£33,000 – £70,000	Usually combined with a rear dormer
Mansard	£38,000 – £90,000	Maximum space. Almost always needs planning permission
L-shaped dormer	£55,000 – £100,000	Victorian and Edwardian homes with a rear addition
Cost per square metre	£1,200 – £2,500 per m²	Up to £3,000 for a high-specification finish
En-suite bathroom	Adds £6,000 – £15,000	Depends on spec and soil stack run
Loft staircase	£2,000 – £4,000	Where it lands is the biggest design constraint
Structural engineer	From around £395	Required for every conversion
Loft insulation (to 270mm)	£700 – £1,200	100mm between joists, 170mm across
Loft boarding	£70 – £100 per m²	A 15m² loft on a raised system is around £1,050
Loft ladder installation	£250 – £400 fitted	To an existing hatch
Loft hatch installation	£150 – £400	Relocating a hatch is around £405

What Our Loft Specialists Do

Before You Book a Loft Conversion

• Measure the head height first. Run a tape from the top of the ceiling joist to the ridge. You want at least 2.2m for a conversion to work without altering the roof, and Building Regulations require 2m of clearance over the staircase.
• Permitted development has hard limits. The additional roof volume must not exceed 40 cubic metres for a terraced house or 50 for a detached or semi. The allowance is cumulative, so previous roof work counts against it — including a previous owner’s. Front-facing dormers, flats, listed buildings and conservation areas need full permission.
• Building Regulations approval is required for every loft conversion, including those under permitted development. They are two separate processes.
• Fire safety is often the biggest hidden cost. A third storey generally means a protected escape route — fire doors, upgraded ceilings and mains-linked alarms. It affects rooms outside the loft and is a common reason cheap quotes come in cheap.
• Serve Party Wall notices in good time. If you are terraced or semi-detached, generally two months before work starts. Leaving it late is a very common cause of delay.
• Be careful about spray foam loft insulation. Many UK mortgage lenders now decline or restrict lending where spray foam has been applied to roof timbers, and surveyors routinely flag it. Removal typically costs several thousand pounds. Mineral wool carries none of these complications.

Loft Conversion FAQs